Stasis, also known as detention (Portal) or suspension (Portal 2), is a state of suspended animation in which a person subject to the process is chronologically frozen. The subject is unconscious, and cannot move, think, or speak.
Stasis has some known side effects. Being in stasis for a period of a couple months may cause cognitive deterioration, while staying subject to it for a couple years may cause serious brain damage. The effects of being under stasis for a short period of time are unknown.
At the beginning of Portal the player character, Chell, wakes up from stasis in the Relaxation Vault. The duration of her brief detention was undefined. This is the only appearance of stasis in Portal.
Portal 2: Lab Rat
In the Portal comic Lab Rat, which is set between Portal and Portal 2 , shows stasis on two occasions. The Party Escort Bot puts Chell into Extended Relaxation. Doug Rattmann realises that the whole of the test centre's power had run out and patched Chell's cryo-chamber into the reserve power to allow her to live with the consequence of her being in stasis indefinitely. In Rattmann's words "So it's the long sleep... or the long sleep". At the end of the comic, Rattmann then goes into short term stasis after being shot by a turret.
In Portal 2 the player character wakes up from Stasis after 50 days and is asked by the Announcer to do a mandatory physical and mental wellness exercise. The player goes into stasis again. The player then reawakens after an extremely long time, too long for the announcer to compute. This is the only appearance of stasis in Portal 2.
The bed in the relaxation vault is evidently some kind of medical equipment. At the front there is a screen and near the back there are canisters of a undefined substance. This is very different to the bed found in The Extended Relaxation Centre which is made to look like a normal bed and does not show any signs of how it works .